Filaments of a synthetic organic polymer

ABSTRACT

A POLYAMIDE YARN IS DESCRIBED COMPRISING AT LEAST ONE POLYAMIDE FILAMENT WHICH HAS AN AS-SPUN MOLECULAR ORIENTATION EXHIBITING AN X-RAY DEFFRACTION PATTERN OF CONCENTRIC RINGS IN WHICH THE ORIENTATION FACTOR OF THE INNER RING MINUS THE ORIENTATION FACTOR OF THE OUTER RING IS GREATER THAN 0.2. THE ORIENTATION IN THE AS-SPUN POLYAMIDE FILAMENT IS OBTAINED BY THE ADDITION OF A SMALL AMOUNT OF A POLYAMIDE NUCLEATING AGENT IN FINELY DIVIDED PARTICLE SIZE PRIOR TO SPINNING INTO A FILAMENT. THE POLYMERIC NUCLEATING AGENT IS PREFERABLY A POLYAMIDE HAVING A HIGHER MELTING POINT THAN THE MELT HOLDING TEMPERATURE OF THE FILAMENT FORMING POLYAMIDE.

Jan. 19, 1971 p, R. THOMAS FILAMENTS OF A SYNTHETIC ORGANIC POLYMER Filed Sept. 14, 1966 2 Sheets-Sheet 1 FIG.

M m u n Cb 3525a 292E533 52 CDQLlNG RATE "(pumlm /A/V/V 7 0 8 P5 nee P4 sow/m 50/ 51 MM United States Patent Office 3,555,805 FILAMENTS OF A SYNTHETIC ORGANIC POLYMER Peter R. Thomas, Pontypool, England, assignor to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain Filed Sept. 14, 1966, Ser. No. 579,273 Claims priority, application Great Britain, Sept. 14, 1965, 39,122/65 Int. .Cl. D01f 1/02, 7/ 04; D02g 3/02 US. Cl. 57-140 Claims ABSTRACT OF THE DISCLOSURE A polyamide yarn is described comprising at least one polyamide filament which has an as-spun molecular orientation exhibiting an X-ray deffraction pattern of concentric rings in which the orientation factor of the inner ring minus the orientation factor of the outer ring is greater than 0.2. The orientation in the as-spun polyamide filament is obtained by the addition of a small amount of a polyamide nuoleating agent in finely divided particle size prior to spinning into a filament. The polymeric nucleating agent is preferably a polyamide having a higher melting point than the melt holding temperature of the filament forming polyamide.

This invention relates to filaments derived from polyamides i.e. condensation polymers wherein amide groups form an integral part of the polymer chain.

Polyamide filaments are most rapidly and economically obtained on a large scale by the extrusion of a molten mass of the polyamide, and, melt-spinning, as it is commonly referred to, has attained pre-eminence as the commercial method of manufacturing polyamide filaments.

In one typical melt-spinning method, the polyamide prepared by a conventional polymerisation process is cooled, broken into chips and dried. The chips are then melted and the molten fibre-forming material continuously pumped, by means of a metering pump, through a filter pack generally containing a fine-grained particulate material, and then extruded through the orifices in a spinneret under the pressure exerted on it at the back of the spinneret by the action of the pump. The freshly extruded filaments, which on emergence from the spinneret orifices are in the form of a viscous molten liquid, cool and elongate as they move away from the spinneret, the cooling often being assisted by a transverse or cocurrent stream of air flowing in a quenching chamber, often referred to as the chimney. The cooled and solidified filaments may then, as in polyhexamethylene adipamide (6.6 nylon) spinning, pass through a steam conditioner tube prior to passing over finish application rolls. Finally the filaments are wound up on a suitable support. In order that the filaments should achieve their maximum strength it is necessary that they be stretched by several, usually at least three, times their original length. This stretching normally referred to as drawing is carried out by passing the filaments between two sets of rotating rolls, the second set of rolls, drawrolls, rotating at a higher peripheral speed than the first, set, feed rolls, to impart the desired degree of stretch to the filaments which are then wound up on a bobbin or like support. A snubbing pin may be positioned between the two sets of rolls to locate the point of draw.

The point below the spinneret face at which the molten filaments solidify, hereinafter forconvenience referred to as the solidification point, represents the point at which the mobility of the polyamide molecules has decreased, with the falling tmeperature, to such an extent that the viscosity of the material is sufiiciently high to preclude,

3,555,805 Patented Jan. 19, 1971 at least temporarily, for changes may subsequently occur as a concomitant to crystallisation, any further elongation of the filaments, thereby substantially stabilising the denier thereof. The temperature associated with the solidification point is below the normal melting point of the bulk solid polymer, and the spun filamentary material is therefore supercooled. Generally a high degree of supercooling of the spun filamentary material at the solidification point is considered to be desirable in, for example, minimising the growth of large spherulites which are wellknown to have adverse effects on filament processability. In order to obtain the required high degree of supercooling it is necessary to impose a limit on the maximum spinning speed achievable in a particular spinning process, the actual value of this limit being dependent upon factors such as spun filament denier.

The elongation which the freshly extruded filaments undergo before solidification is generally referred to as the draw down. As well as reducing the denier of the filaments draw down also causes the molecules in the filaments to become oriented to some degree and there is some increase in the degree of orientation even after solidification. This orientation causes well-known birefringence effects to become visible when the filament is viewed transversely through a polarising microscope. Birefringence in the as-spun filaments, that is filaments which have not been subjected to an additional drawing process, is called the spun birefringence and its value may be determined by known techniques using a polarising microscope and a Berek compensator.

That a filament exhibits a measurable birefringence indicates that the segments of the polymer molecules which possess an intrinsic optical amisotropy must have a preferred orientation relative to the filament axis. Other techniques have to be employed to obtain more precise information on the nature of the preferred orientation. As is well-known one such technique is by means of the wide-angle X-ray Laue pattern from the fibre.

The Laue pattern exhibited by the fibre comprises two major rings, an inner and an outer ring, which are reflections from the principal paratropic lattice planes of the crystalline structure. The intensities of these rings (M) at meridian, the meridian being a straight line on the X-ray film parallel to the fibre direction and passing through the position of the primary X-ray beam, and (E) at equator, the equator being a straight line on the X-ray film perpendicular to the fibre direction and passing through the position of the primary X-ray beam, can be determined and orientation factors M E calculated. For convenience these orientation factors are designated 0 for the inner ring 0 for the outer ring, by which terms these factors will be referred to hereinafter.

In normal spinning of 6.6 nylon, for example, the orientation factors 0, and 0 as defined above for the asspun yarn are usually negative and often differ slightly in numerical value. The negative sign indicates that the c axis of the crystal lattice unit cell, i.e. the molecular chain axis, is becoming oriented towards the filament axis, i.e. the structure may be described as having a preferred 0 axis orientation. The degree of orientation is generally low as indicated by the magnitude of the spun birefringence. In a fully drawn yarn of course the c axis orientation is high and O and O tend to the value of 1,

If the orientation process is simply a progressive alignment of the molecular chains more and more parallel to the filament axis then O O for all degrees of orientation. However, this condition frequently does not exist and it is considered that when (O,0 differs from zero then 3 the orientation process is more complex and it is useful to consider the size and magnitude of (O, In normal as-spun yarn of 6.6 nylon, for example, O is often numerically slightly larger than 0 and then (0 -0 is small but positive, that is, it has a value in the range 0 to 0.2.

Generally the magnitude and nature of the spun orientation will control the degree of extrusion available in the drawing process to achieve the desired drawn yarn extension at break. It is well-known that the draw ratio subsequently required to be applied to an as-spun yarn to produce a drawn yarn having the desired extension at break, decreases as the spinning speed is increased.

Surprisingly we have now found that polyamide filaments can be obtained by melt spinning which, in the as-spun state, have values for (O -0 greater than 0.2 and that these filaments can be spun at higher speeds, i.e. wind up speeds, with consequent increase in productivity, than the previously known filaments having lower values (O -0 Such filaments exhibit a lesser degree of supercooling at the solidification point in the spinning process under otherwise comparable conditions, which has obvious process advantages.

Furthermore we have found that as-spun polyamide filaments in which (0 -0 is greater than 0.2, and which have been spun at spinning speeds greater than about 1,500 ft. per minute, may be drawn at higher draw ratios than as-spun filaments in which (0 -O is less than 0.2 and which are spun at the same speed. Thus these filaments exhibit orientation characteristics which allow a further increase in spinning productivity to be obtained.

The invention will be more clearly described by reference to the drawings in which:

FIG. 1 is a representation of an X-ray pattern obtained from an as-spun nylon 6.6 fiber of the present invention indicating reflections from the principal paratropic lattice planes which are indicated by the Miller indices of 100.010 and 110;

FIG. 2 is a representation of an X-ray pattern obtained from a normal as-spun nylon 6.6 fiber;

FIG. 3 graphically illustrates the solidification point plotted against the cooling rate of various nylon 6.6 polymers with varying percentages of nucleating agent compared to no nucleating agent;

FIGS. 4 and 5 graphically illustrate the variation in DTA freezing point of nylon 6.6 on linear and leg scales respectively, wherein the nylon 6.6 contains different amounts of copolymer nucleating agent.

When the magnitude of (0 0 is large, i.e. greater than 0.7, 0 has a positive value and 0 a negative value. This condition implies that the a axis of the crystal lattice unit cell is becoming oriented towards the filament axis, i.e. the structure may be described as having a preferred a axis orientation which contrasts with the preferred 0 axis orientation of the previously known as-spun polyamide filaments.

Accordingly therefore, from one aspect, the present invention provides a yarn comprising one or more undrawn polyamide filaments having molecular orientations exhibiting X-ray reflection patterns in which (0 -0 is greater than 0.2. Preferably (0 -0 is greater than 0.7 and even more preferably 0 is greater than zero.

A feature of the present invention is that the change in spun orientation of the filaments enables a draw ratio for a required extension at break in the drawn yarn to be achieved which is largely insensitive to spinning speed.

The values of O and 0 are determined in the following manner.

The yarn sample is wound as a parallel bundle of fibres on a fibre sample holder, which is then mounted in an evacuatable X-ray camera using a flat plate film. The camera is evacuated for a minimum period of 5 minutes (to a vacuum better than 0.2 mm. of Hg), and an exposure of 15 minutes at 40 K and 5 mai given to 4 each sample, the cameras being continuously evacuated during the exposure. Ni filtered CuKa radiation is used from a sealed X-ray tube operating in a Philips PW1008/ 3O generator.

The exposed film is processed as follows: 5 minutes in Ilford PQX-l X-ray film developer (at 20 C.), 1 min. wash, 4 mins. in M & B Perfix fixer (at 20 C.), followed by a 30 min. or more wash, to give a maximum optical density on the film of approximately 1.0.

Using a Joyce-Loebl double beam recording microdensitometer (Model E.l2 Mk III), diametrical scans are made across the equator and meridian of the diffraction pattern, the fibre axis being along the meridian. The two records are produced superimposed on one chart. A common background is drawn in before measurements are made of the intensity (E and M respectively) at the equator and meridian for the two main reflections. The ratios are then determined.

FIG. 1 of the drawings is a representation of an X-ray pattern obtained from an as-spun filament of 6.6 nylon of the present invention, indicating the reflections from the principal paratropic lattice planes of the crystalline structure which are used in the determination of the values of O and 0 FIG. 2 of the drawings is a representation of an X-ray pattern obtained from a normal as-spun yarn of 6.6 nylon. Comparison of the figures shows the nature of the orientation differences of the two filaments.

As examples of polyamides with regard to which the present invention is especially useful there may be mentioned polyhexamethylene adipamide (6.6 nylon) and polyhexamethylene suberamide (6.8 nylon).

The desired orientation may be induced in the as-spun polyamide filaments by the incorporation of at least 0.05, preferably 0.5 to 1.5 percent by weight of a finely divided nucleating agent in the polymer prior to spinning. The nucleating agent is preferably polymeric and should have an optical melting point greater than the melt holding temperature at spinning. Preferably the optical melting point of the polymeric nucleating agent is at least 10 C. or even more preferably at least 30 C., above the melt holding temperature at spinning.

The optical melting point of the polymeric nucleating agent is determined by observing under a microscope a sample of the material supported between glass slides that rest on an electrically heated stage; the melting point is taken as the temperature at which the optical birefringence of the sample disappears.

The melt holding temperature at spinning is defined as the temperature at the base of the melt pool above the booster pump in a conventional melt spinning unit such as is used in the manufacture of 6.6 nylon.

It is known to incorporate nucleating agents in polymers such as polyamides which are to be used in moulding and for making films, for example, to improve, inter alia, the transparancy of the resultant product; However it has not been known to deliberately incorporate nucleating agents in polymers which are to be melt spun into textile filaments.

According to another aspect, therefore, the present invention provides a process for the manufacture of a yarn consisting of undrawn polyamide filaments comprising incorporating a finely divided nucleating agent in a polyamide, forcing the molten polyamide containing the nucleating agent through a filtering medium, extruding the said polyamide through orifices contained in a spinneret plate and winding up the filaments.

Preferably the polymer contains at least 0.05% by weight, and more preferably 0.5% to 15% by weight of the nucleating agent.

Although it is preferred that the polymer should contain at least 0.05% of the nucleating agent, the actual lower limit for the concentration of the nucleating agent will depend upon the fineness of its state of division and may well be less than 0.01% by weight.

The term nucleating agent is to be understood to refer to solid substances which, when present in a finely divided state i.e. having a particle size less than 0.4 diameter in the as-spun polyamide filaments, induce the formation and growth of a crystalline texture which does not exhibit in the polarising microscope at the extinction position any discrete resolvable patterns characteristic of the well-known spherulities, i.e. the so-called Maltese cross pattern. Spherulite growth, if present, must therefore be limited to sizes approximately equal to or below the wavelength of visible light that is below about 1.5 in diameter.

Polyamides having optical melting points greater than and preferably at least C. above the melt holding temperature at spinning of the base polymer may usefully be employed as nucleating agents. Especially affective are polyamides or copolyamides containing an aryl group in the polymer chain. As examples of this class of nucleants there may be mentioned polyamides comprising poly- (methylene) terephthalamide where x is an integer between 2 and 12 such as poly hexamethylene terephthalamide (6.T nylon), poly octamethylene terephthalamide (8.T nylon), poly decamethylene terephthalamide (10.T nylon) and poly dodecamethylene terephthalamide (12.T nylon). Copolyamides ofthe terephthalamides with other polyamides, e.g. poly hexamethylene adipamide/poly hexamethylene terephthalamide (6.6:6.T) copolymer, polyhexamethylene adipamide/ poly octamethylene terephthalamide (6.6:8.T) copolymer, poly hexamethylene adipamide/poly decamethylene terephthalamide (6.6:10.T) copolymer, poly epsilon caprolactam/poly hexamethylene terephthalamide (6:6:T) copolymer and poly hexamethylene suberamide/poly hexamethylene terephthalamide (6.8:6.T) copolymer are particularly useful, the 6.6:6.T copolymer being the preferred nucleating agent for 6.6 nylon. The proportions of the aliphatic to aryl containing polyamides in the copolyamides to give the most effective nucleating agent for any given polyamide have to be determined by experiment, for the effective nucleation of 6.6. nylon by 6.6:6.T copolymer it is thought that the copolymer should contain at least 30% by weight, and preferably at least 40% by weight of polyhexamethylene terephthalamide. Also effective as nucleating agents are poly p-xylyene adipamide and its copolymers with 6.6 nylon, and poly hexamethylene hexahydroterephthalamide and its copolymers with 6.6. nylon.

In addition to a nucleating agent the filaments of the present invention may also contain the usual range of additives such as delustering agents, pigments, antioxidants, stabilisers against the elfects of heat and light, and so on and up to about 5% by weight of another polyamide.

It has been observed that the filaments of this invention have a higher temperature at the solidification point in the spinning chimney i.e. show a lesser degree of supercooling, than previously known filaments. This effect can be readily verified while the filaments are being produced by chopping samples from the filament in either molten or solid form using known methods. After determination of the solidification point by this method the temperature associated with this point can be measured utilising a thermocouple or infrared pyrometer.

This increase in the temperature at the solidification point of the filaments in the chimney can be assessed more conveniently by the use of differential thermal analysis (D.T.A.) since, at a defined rate of cooling, the freezing point of a nucleated polymer is higher than the freezing point of the base polymer. This increase is usually of the order of at least 5 C. and may be as much as 10 C. D.T.A. freezing point can therefore be used to give an indication of whether or not a polyamide has been nucleated in a manner which will, when the polymer is melt spun, yield an undrawn yarn having the defined parameters. For example polyhexamethylene adipamide has a D.T.A. freezing point of about 223 C.; the inclusion of 1% of a (50:50) 6.6:6.T copolymer may raise the said freezing point to 234 C.

D.T.A. freezing point is determined using a differential scanning calorimeter DSC-l available from the Perkin- Elmer Corporation, Norwalk, Conn., USA. in combina tion with a recorder, the instrument sold as Model W by Leeds and Northup Co. being perfectly satisfactory. Differ ential power (i.e. the difference between the power supplied to test and control samples to maintain them at the same temperature and with the same rate of increase or decrease of temperature) which is equivalent to temperature, since the temperature increase or decrease is linear with time, is automatically plotted against time on the recorder. The temperature scale is automatically marked out on the side of the chart paper. In most instances it is convenient to determine on the same sample both its melting point, at a 2 C. per minute linear rate increase of temperature, and the solidification point, i.e. the freezing point of the molten material, using a 64 C. per minute rate of fall in temperature, although for the purposes of this specification, the latter point, which can be determined more accurately than the former, is generally the more significant.

The detailed method employed in conducting the D.T.A. {est using the above rates of heating and cooling is as folows:

A sample of 5-15 mg. in weight is cut from polymer chip with a razor blade and sealed in an aluminum sample pan (as supplied by Perkin-Elmer) and placed in the DSC-1 pan holder.

With dry nitrogen at room temperature flowing through apparatus at 25 cc./min. the sample temperature is raised using manual control fairly rapidly (taking about 10 secs. for 200 C.) to 232 C. It is left at this temperature for 2 mins. for the whole sample to reach equilibrium, then the scanning speed of the instrument is set at 2 C./min., and the temperature of the sample automatically raised. The machine is left to run until the melt transition temperature has been passed when the curve which is being traced out by the recorder pen straightens out.

The temperature is then raised manually to the holding temperature, which, for any particular polymer, is the melt pool temperature of a spinning unit, e.g. 285 C. in the case of 6.6 nylon. The sample is held at this temperature for 2 min. Then the scanning speed is set to 64 C./min., and the temperature automatically lowered at the required rate. When the transition is finished the temperature is lowered manually down to room temperature.

To take readings from the recorder chart so obtained, a ruler is placed along the portion of the trace immediately prior to the transition to establish the best straight base-line that the slightly uneven curve will fit onto, and the transition (solidification and/or melting) temperature is taken to be that point at which the curve first moves away from the base-line. This can be determined to better than 1 C accuracy.

The test is also used to determine the freezing point of undrawn i.e. as-spun filaments.

Various methods, some of which will now be described in more detail, may be employed for introducing the nucleating agent into the polyamide.

For instance, in one method, herein for convenience referred to as the solution blending method, solutions of 7 to a further blending with additional polyamide. This further blending may be achieved by chip blending, i.e. by addition of chips of the master batch to the required amount of polyamide chips, or by chip coating, that is forming a paste of the master batch and using this paste to coat polyamide chip.

The nucleating agent can also be incorporated into the polyamide in the correct proportions by a melt-dispersion process, for example, by passing the mixed components through a heated screw extruder optionally combined with a metering pump, for instance a Duplex pump. This method may be used to form a master batch of the nucleating agent in the polyamide which may then be further blended with the required amount of additional polyamide by chip blending or chip coating.

The nucleating agent could be incorporated into the polyamide by introducing it into the autoclave during the polymerisation of the polyamide forming salt, or into the polymerisation coil in a continuous polymerisation process.

In processes involving the melt-dispersion of a nucleating agent in a polyamide it is most important that the temperature does not exceed a limit which is dependant upon the optical melting point of the nucleating agent as otherwise the effectiveness of the nucleating agent is lost. We have found that the melt-dispersion temperature should not exceed 1.08, and preferably 1.04, times the optical melting point of the nucleating agent.

Any other convenient method of mixing, such as by the use of a Banbury mill, may be employed. It is most important, however, that the nucleating agent be well dispersed in the polyamide since poor dispersion will result in an inadequately nucleated polymer and the novel filaments of the present invention will not be obtained therefrom.

Nucleated polymer may be extruded into filaments using any conventional spinning method involving filtering the polymer through a conventional filter pack prior to extrusion through spinneret orifices at normal temperatures, e.g. of the order of 290 C. as is normally employed in spinning nylon 6.6.

The following examples are illustrative of the ways in which the novel filaments of the present invention may be prepared and of the various compositions of the said filaments. It is to be understood that the examples are not intended to in any way limit the scope of the invention.

EXAMPLE 1 Preparation of a (50:50) 6.6:6T copolymer nucleating agent Equivalent molecular proportions of hexamethylene diammonium adipate and hexamethylene diammonium terephthalate and a small amount of water (used to maintain homogeneity), were mixed together and heated, with continuous agitation, in an autoclave at a temperature of Incorporation of the copolymer nucleating agent into 6.6 nylon The copolymer additive was then incorporated into 6.6 nylon by a solution blending method as follows:

72 gm. of the copolymer additive were dissolved in 648 gm. of 90 percent aqueous phenol (10 percent weight by weight solution) by refluxing and stirring under an atmosphere of nitrogen. Another solution containing 1,368 gm. of polyhexamethylene adipamide having a relative viscosity of 40, was made by dissolving the polyamide in 12,312 gm. of 90 percent aqueous phenol (10 percent weight by weight solution).

The two solutions were mixed, by stirring together, at a temperature of around 40 C., in amounts such that the final ratio of solutes was one part of weight of the copolymer nucleating agent to 19 parts of 6.6 nylon. The homogeneous phenol solution was poured into methanol, and the precipitate filtered off and washed with methanol, and then boiled with water for several days to steam distill off the residual phenol. The precipitate, after drying was in the form of a fairly fine powder (master batch powder).

940 gm, of the master batch powder was homogenised with 2 litres water using an Ultra Turrax high speed mixer to form a paste. 280 gm. pigmentary nylon base (20% pigmentary nylon-avery finely divided low molecular weight 6.6 nylon+% water) was also added and mixed in with the master batch powder. This was necessary to ensure satisfactory adherence of the powder to the polymer chip in the final chip coating operation, particularly at the relatively high level required.

The paste prepared as described above was chip coated onto standard production 6.6 nylon chip (relative viscosity 40, 0.3% TiO content) in a Gardner mixer using 8 lb. polyamide chip so that the ratio of master batch powder to the 6.6 nylon chip was 1:4 giving a final level of 1 percent of the copolymer nucleating agent of the coated chip for spinning. 1

The resultant polymer had a D.T.A. freezing point of 234 C. while a control polymer without nucleant had a D.T.A. freezing point of 223 C.

The polymer was melted in a gravity melter and the melt extruded through a 10 hole spinneret (each hole being 0.013 inch in diameter) into filaments at a rate of approximately 0.054 1b. total polymer per minute at a spinning temperature of 289 C. The filaments were spun into a quenching chamber wherein they were cooled by a transverse stream of air and in which they became solid. The 10 filament yarn so obtained, in which the filaments were each 9 denier, was collected at ambient temperature and relative humidity at a speed of 3930 feet per minute in the form of a yarn package. To provide the comparative information a control yarn, derived from polyhexamethylene adipamide chips having a relative viscosity of 40 and containing 0.3 percent Ti0 as a delustrant but no copolymer nucleating agent, was spun and collected under identical conditions. The yarn containing the filaments of the present invention had a birefringence value of 0.0101 and the control yarn a value of 0.0185. Both yarns were drawn using a production type drawtwister operating at a drawing speed of 1520 feet per minute. The draw ratios were adjusted for each yarn to give drawn yarn of 30 denier with 0.5 Z turn per inch twist and with a nominal extension at break of approximately 30 percent.

The yarn containing the filaments of this invention had to be drawn at a draw ratio of 4.40 to produce a yarn with an extension at break of approximately 30 percent while the same extension at break could be obtained in the control yarn by drawing it at a draw ratio of only 3.12. The increase in spinning productivity, arising from the opportunity which was afforded of using larger throughputs of the polymer, was therefore of the order of 40 percent.

Without limiting the invention to any particular theory it is believed that the incorporation of a nucleating agent such as that described in Example 1 in a polyamide influences the development of crystallinity in filaments spun from the molten polymer to the end that the filaments solidify nearer the spinneret plate than unnucleated filaments, with a reduced degree of supercooling at the solidification point. The nucleant also causes the formation of a large number of small optically birefringent regions uniformly distributed throughout the filament to the exclusion of large spherulites, which regions, when viewed in polarised light, do not exhibit any resolvable pattern of preferred orientation such as the well-known extinction patterns normally associated with spherulitic structures and are usually less than 1 micron across.

The influence of the nucleating agent employed in Example 1, i.e. a (50:50)6.6:6T copolymer, at varying concentrations, on the D.T.A. freezing point of 6.6 nylon is shown graphically in FIG. 3, in which freezing point is plotted against rate of cooling. The curves in FIG. 3 are identified as follows:

Curve A-polyhexamethylene adipamide with no copolymer nucleating agent Curve Bpolyhexamethylene adipamide with 0.05 percent nucleating agent Curve Cpolyhexamethylene adipamide with 0.1 percent nucleating agent Curve D-polyhexamethylene adipamide with 0.3 percent nucleating agent Curve E--polyhexamethylene adipamide with 1 percent nucleating agent Curve F-polyhexamethylene adipamide with 3, and

percent nucleating agent The figure shows that the freezing point of the polymer increases with increase in concentration of the nucleating agent up to between 1 and 3% levels, there being little detectable change as the concentration is increased from 3 to 10% (curve F).

FIGS. 4 and 5 show graphically on linear and leg scales respectively, the variation in D.T.A. freezing point of 6.6 nylon containing ditfering amounts of the copolymer nucleating agent. The freezing points being determined at a fixed rate of cooling, i.e. 64 C./min. Little change in freezing point is seen until the concentration of the nucleating agent reaches at least the 0.01% level, the freezing point then increases rapidly up to about the 2% level after which there is little or no increase. A copolymer nucleating agent concentration in the range 0.5 to1.5% would appear to be a satisfactory working range.

Although the above-mentioned graphs were constructed from results obtained from bulk polymers, the conclusions are equally applicable to filaments spun from the polymer which would normally be cooled at a rate exceeding 64 C./min.

In the further examples described hereinafter the in crease in productivity is indicated by the productivity ratio (P.R.) which is defined as:

Draw ratio to yield 30% extension at break for a filament containing nucleating agent Draw ratio to yield 30% extension at break for a filament without nucleating agent The as-spun yarns are also characterised by reference to the draw ratio at a nominal stress of 0.5 g./d. This parameter is determined by measuring the drawing tension of the yarn when drawn at a draw roll speed of 800 f.p.m. at draw ratios of 1.25, 1.50, 1.75, etc. until the yarn breaks. The values of drawing tension are converted to nominal stress by the relationship:

drawing tension nominal stress= spun demer of as-spun filaments containing a nucleating agent with.

as-spun filament without a nucleating agent, clearly shows that higher draw ratios can be achieved with the former.

In order to obtain the filaments of the present invention it is essential that the nucleaing agent remain as discrete particles in the polymer during spinning and also during melt dispersion when this method is used to incorporate the nucleating agent in the polymer. It is also important under these circumstances that the holding time of the 10 polymer containing the nucleating agent in the molten state during melt-dispersing and spinning be kept as short as practicable to limit the degree of amide interchange taking place between the polymer and the nucleating agent which would elfectively destroy the latter.

For the above reasons it is clear that a polymeric nucleating agent should have an optical melting point at least above the melt holding temperature at spinning. Preferably the optical melting point of the nucleating agent is at least 10 C. or even more preferably at least 30 C. above the melt holding temperature at spinning.

A polymeric nucleant which has an optical melting point which is considered to be too low to be wholly effective in a particular polyamide system, may have its melting point raised by a heat treatment. Thus it has been established that the optical melting point of a (50:50)6.6:6T copolymer can be raised from 325 C. to 344 C. by heating at 325 C. for 1 hour under steam at atmospheric pressure.

EXAMPLES 2, 3 AND 4 In these examples the base polyamide was 6.6 nylon (40.R.V. containing 0.3% TiO and the nucleating agent a (50:50)6.6:6T copolymer.

The spinning speed, in these and all subsequent examples, was 3930 f.p.m. unless stated to be otherwise.

The nucleating agent was prepared by mixing together in the presence of a small amount of water, equivalent molar preparations of hexamethylene diammonium adipate and hexamethylene diammonium terephthalate. The mixing was carried out in an autoclave with continuous agitation at a temperature of 250 C. and a pressure of 510 psi. for 2 hours. The low molecular weight polymer was further polymerised in the solid state by heating at 290 C. in steam for a period of 5 /2 hours. The optical melting point of the copolymer was 330 C.

Dispersion of the nucleating agent in 6.6 nylon was carried out using the general procedure described in Example 1 with various ratios of base polymer to nucleant employed in the preparation of the master batch. Details of the dispersion of the copolymer nucleating agent in 6.6 nylon base polymer are given in Table 1 below:

The polymers were spun into 10 filament yarns at a spinning speed of 3930 ft./min. at a spinning temperature of 290 C. and subsequently drawn at 1500 ft. min. Details of spun yarn properties and draw ratios are given in Table 2.

EXAMPLES 5, 6 AND 7 The present examples illustrate a method of incorporating a nucleating agent in the base polymer by meltdispersion. The base polymer and a (50:50)6.6:6T polymeric nucleating agent were initially blended together at various nucleant to base polymer ratios by mixing the polymer and nucleant together in the dry state and then melt-dispersing the nucleant by passing it through a screw extruder. The molten polymer containing the disposed nucleating agent was cooled, chipped and blended with the base polymer chip to give the correct nucleant concentration. The screw extruder used had a screw diameter of inch and ran at a speed of 25 r.p.m. The maximum temperature of the barrel of the extruder was 325 C. and the throughput 30 ml./min. giving a polymer transit time in the extruder of approximately 1 minute.

The final chip blend was spun and drawn under the conditions used in the previous experiments. Details of the processes and yarn properties are given in Table 3.

TABLE 3 Example 5 6 7 Melt dispersing: I

Ratio nucleating agent to base polymer in master batch 1:99 1:19 1 :9 Temperature, C 315 325 325 Chip blending:

Ratio melt mix to base polymer 1:4 1:9 Concentration of nucleating agent, percent- 1 1 1 D.T.A. freezing point of nucleated polymer,

C 231 229 231 S un yarn properties:

p Denier/filament 13.0 13. 7 13. 6 Birefringence" 0 0128 0. 0113 Oi 0.24 0.08 0.26 00" 0. 60 O. 53 0. 68 O1O 0.84 0.61 0.94 D.I.A. freezing point, C 231 229 231 Draw ratio for 30% extension at break. 4. 12 4. 20 4. 40 Draw ratio at nominal stress of 0.5. 4. 25 3. 84 3.12 Productivity ratio 1. 32 1. 33 1.

12' polymer by the melt-dispersing method. Details of the polymer preparation and spun and drawn yarn properties are given in Table 4.

TABLE 4 Example 8 9 Melt dispersing:

Ratio nucleating agent to base polymer 1:19

Temperature, C 325 Chip blending:

Ratio melt mix to base polymer 1:4

Concentration of nueleant agent, percent-.- 1.0

D.T.A. freezing point of polymer, C 206 198 Spun yarn properties:

Denier/filament 9. 2 9 0 Birefringence 0. 0112 Oi-O 0. 60 0. 2

D.T.A. freezing point, C 205 201 Draw ratio for extension at break. 3. 88 2. 78 Draw ratio at nominal stress of 0.5 2. 75 1. 10 Productivity ratio 1. 39 1. 0

Examples 10, 11 and 12 illustrate the efiectiveness in 6.6 nylon of different polyamide nucleating agents containing a terephthalamide linkage in the polymer chain, Example 13 is a 6.6 nylon control included for the purpose of comparison. Spinning and drawing of uncleated polymers were carried out under the conditions previously described. Details are given in Table 5.

TABLE 5 Example 10 11 12 13 Nueleating agent (:50)6.6:6.T Method of dispersing nucleating agent- Temperature of melt dispersing, C 325 Ratio nucleating agent to base polymer in master batch 1:9 1:19 Chip blending/chip coating ratio, master batch to base polymen. 1:9 1:4 Concentration of nucleating agent, percent 1.0 1. 0 D.T.A. freezing point of polymer, C 234 Spun yarn properties:

Denier/filament 13. 6 9. 1 9. 1 9. 2 Birefringence 0. 0068 0. 0123 O: 0.26 0.0 0.01 0.56 On 0. 68 0. 28 0. 59 0. Or-On 0.94 0. 37 0.58 0.09 D.T.A. freezing point, 231 235 232 226 Draw ratio for 30% extension at b 4. 12 3.77 3.81 2. 94 Draw ratio at nominal stress of 0.5-. 4. 25 4.10 3. 30 1.25 Productivity ratio 1. 32 1. 21 1. 22

1 6.1 nylon. 2 10.T nylon. 3 Melt dispersing.

4 Solution blending (the solvent was aqueous phenol and precipitant methanol).

The following examples 14-19 compare the effectiveness of various concentrations, from 0.01% to 5.0% by Weight of the preferred nucleating agent (50:50)6.6:6T nylon, in 6.6 nylon containing 0.3% T10 Details are shown in Table 6.

TABLE 6 Example 14 15 16 17 18 19 Method of dispersing nucleating agent Temperature of melt dispersing, "C 325 325 Ratio nucleating agent to base polymer in master batch 1:19 1:19 1:19 1:2 1: 19 Chip blending/chip coating: ratio master batch to base polymer 1:499 1:9 1:4 1:32. 2 Concentration of nncleating agent, percent 0. 01 0. 5 1. 0 2. 0 5.0 D.T.A. freezing point, C 232 233 Spun yarn roperties:

Denier filament 10. 9 12. 4 13. 1 13. 4 13. 1 9. 1 Birefringence 0. 0103 0. 0093 0. 0125 0. 0110 0. 009 O; 0. 37 0. 07 0. 15 0. 21 0. 17 0. 05 0.7 0. 51 0. 38 0. 53 0. 57 0. 49 0. 61 O:-O., 0. 14 0.45 0. 68 0. 97 0. 56 0.66 D .T.A. freezing p0 229 231 229 231 232 Draw ratio for 30% extention a 3. 52 4. 05 4. 26 4. 36 4 48 3. 87 Draw ratio at nominal stress of 0.5 1. 88 4. 15 4. 0 3. 90 3. 50 3. 48 1.05 1. 29 1. 37 1. 39 1. 38 1. 24

Productivity ratio 1 Solvent blending: 3 Melt dispersing.

13 The above examples indicate that, in the particular system employed and under the conditions of dispersion used, 0.01% of the nucleating agent is insuflicient to yield filaments according to the present invention. Thus -0 is less than 0.2, there is substantially no increase in productenacity of 4.34 g/d., extension at break of 29.3% and an initial modulus of 26.5 g/d/ 100% extension.

EXAMPLE 24 This example illustrates the effect of melt-dispersing tivity, and the draw ratio at a nominal stress of 0.5 g./ d. 5 a P Y I nu ating agent, having an and draw ratio for 30% extension at break is lower than P melting PQint 0f 'a in nylon at a high for the remaining examples which illustrate the invention. temperature. Details are given in Table 9. There are however indications that nucleation had oc- TABLE 9 curred since the spun yarn has an increased D.T.A. freez- 1O ing point compared with the control yarn of Example 13. Temperature of melt-dispersion, C.: 361 The results also indicate that there is no advantage in Ratio nucleating agent to base polymer: 1:99 using a concentration of nucleating agent exceeding 0.1%, Concentration of nucleating agent, percent: 1 although in practice a concentration of between about 0.5% and 1.5% would be preferred for purely technical ggg zfig iffifi i 48 reasons associated with obtaining an adequate degree of B1refr1ngence. 0.0128 disperson of the nucleant. O 32 Examples 20, 21 and 22 illustrate the use of diiferent 1 45 proportions of 6.6 and 6.T nylons in the preferred 00- b polymer nucleant at the 1% level of nucleant in 6.6 nyo lon. In Example 20 the nucleating agent Was prepared by Big ia gi fi break 3 12 mixing together aqueous solutions of hexamethylene d1- Draw ratio at nominal Stress of 0.5: 2.78 ammonium adlpate and hexamethylene diammomum ter- Productivit ratio 1 00 ephthalate, in the correct proportions by weight, and poy lymerising the mixture as a continuous process in a coil The temperature employed in melt-dispersing the nusuch as that described in British patent specification No. cleating agent in the polymer was greater than that pre- 924,630. In Examples 21 and 22 the nucleating agents ferred, i.e. 1.08 times the optical melting point of the nuwere prepared by the normal procedure adopted in the Cleating g and ill consequencfi there Was I10 increase batch preparation of 6.6 nylon polymer. The nucleating in productivity and a yarn according to the present in agents were melt-dispersed with the 6.6 nylon to give a vention was not obtained. master batch and the master batch chip blended with 6.6 What we claim is: nylon chips to give a final concentration of 1% by weight 1. A yarn comprising at least one polyamide filament of the nucleating agent in 6.6 nylon. Details are shown having as spun molecular orientations exhibiting X-ray in Table 7. deflection pat-terns in which (O -0 is greater than 0.2

TABLE 7 Example 20 21 22 Ratio nucleating agent to base polymer in master batch 1:99 1:19 1:9 Temperature of melt dispersing, C .l 335 315 95 Ratio master batch to base polymer in chip blend..- 1:4 :9 Ratio 6.6:6.T nylon in nueleant :55 55:45 60:40 Spun yarn roperties:

Denier filament 12. 5 13. 3 9. 0 Bireiringence 0. 0131 0. 0099 0i 0.21 0.10 0. 26 on 0.59 -0.42 -0.52 i0o 0.80 0.26 0.26 D.T.A. freezing point, C 230 231 232 Draw ratio for 30% extension at break. 3. 99 3. 82 3. 43 Draw ratio at nominal stress of 0.5 3. 52 2. 78 Productivity ratio 1. 28 1- 2 11 EXAMPLE 23 A yarn according to claim 1 having molecular orien- This example relates to the manufacture of 6.6 nylon g z ;zg g gigg i fig 323E 1 h 1 1 monofil from polymer containing 1% of (50:50)6.6:6.T g avmg mo ecu ar orientatlons 1n whlch (O -0 is greater than 0.7. copolymer nucleatlng agent. A 1:9 nucleating agent to 4 A am accordin to Claim 1 t 1 t base polymer master batch was prepared by melt dispery g eas sion at 310 C and the master batch chip blended wit one Polyamlde .filament contammg a finely dlvlded more hase polymer in a 1:9 ratio to give the desired con 55 agent dlsposefd therethfiough centration of nucleating agent. The polymer was spun A yaFI1 aWordlng o Claim 4 comprising at least using conventional equipment to give a monofilament. Polyamlde filament COntallllng 05% t0 5% y Spinning speed and filament parameters are shown in Welght of the Tab1e8 6. A yarn according to claim 5 comprising at least TABLE 8 one palyamide filament containing 0.5% to 1.5% by weight of the nucleating agent. Spinning speed, f.p.m.: 2930 7. A yarn according to claim 4 comprising at least Spun denier, d.p.f.: 66 one filament of polyhexamethylene adipamide. D.T.A. freezing point, C.: 233 8. A yarn according to claim 4 comprising at least 0;: 0.33 one filament of polyhexamethylene suberamide. 0 0.51 9. A yarn comprising at least one polyamide filament 0 -0 0.84 containing a polymeric nucleating agent disposed there- Draw ratio for 30% extension at break: 4.20 through and having as spun molecular orientations ex- Since a 66 d.p.f. monofil can normally only be spun hiblting X'ray defleqlon m whlch (01-00). is at speeds up to 1548 f.p.m. it is clear that the presence 70 Sald, polymer? nucleatmg agent bemg of the nucleating agent resulted in a considerable increase finely dlvlded and hfwmg an optlcal melting Pomt greater in productivity at Spinning than the melt holding temperature of the polyamide at The yarn could be drawn at speeds up to 4,500 f.p.m. SPlnnlngusing a snubbing pin heated to 110-125 C. at draw A yarll accofdlllg t0 Clalm 9 havlng molecular ratios of 4.0 to 4.2 to yield a drawn yarn having a orientations in which 0 is greater than 0.

11. A yarn according to claim 9 having molecular orientations in which O is greater than 0.7.

12. A yarn according to claim 9 comprising at least one polyamide filament containing at least 0.05% by Weight of the polymeric nucleating agent disposed therethrough.

13. A yarn according to claim 12 comprising at least one polyamide filament containing at least 0.5% to 1.5 by weight of the polymeric nucleating agent dispersed therethrough.

14. A yarn according to claim 12 comprising at least one filament of a polyamide selected from the group consisting of polyhexamethylene adipamide and polyhexamethylene suberamide.

15. A yarn according to claim 9 wherein the polymeric nucleating agent has an optical melting point at least C. above the melt holding temperature at spinning.

16. A yarn according to claim 15 wherein the polymeric nucleating agent has an optical melting point at least C. above the melt holding temperature at spinning.

17. A yarn according to claim 9 wherein the polymeric nucleating agent comprises 0.05 to 1.5% by Weight of a polymeric material selected from the group consisting of polyamide and copolyamides containing aryl linkages in the polymer chain.

18. A yarn according to claim 17 wherein the polymeric nucleating agent comprises poly(methylene) terephthalamide where x is an integer between 2 and 12.

19. A yarn according to claim 18 wherein the polymeric nucleating agent is polyhexamethylene terephthalamide.

20. A yarn according to claim 18 whereinthe polymeric nucleating agent is polydecamethylene terephthalamide.

21. A yarn according to claim 18 wherein the polymeric nucleating agent is a copolymer of polyhexamethylene adipamide and polyhexamethylene terephthalamide.

22. A yarn according to claim 21 wherein the copolymer contains at least 30% by weight of polyhexamethylene terephthalamide.

23. A yarn according to claim 21 wherein the copolymer contains at least by weight of polyhexamethylene terephthalamide.

24. A yarn according to claim 21 wherein the copolymer consists of equal proportion by weight of polyhexamethylene adipamide and polyhexarnethylene terephthalarnide.

25. A yarn comprising at least one polyamide filament containing a polymeric nucleating agent disposed therethrough and having an as spun molecular orientation exhibiting X-ray reflection patterns in which (0,0,,) is greater than 0.2, said polymeric nucleating agent being finely divided to a particle size less than 0.4 1. diameter, being incorporated in an amount of 0.05 to 1.5% by weight and having an optical melting point greater than the melt holding temperature of the polyamide at spinning so as to be retained in said finely divided solid particle size.

References Cited UNITED STATES PATENTS 3,227,793 1/ 1966 Cipriani 264290UX 3,354,023 11/1967 Dunnington et al. 264-210X 3,379,810 4/1968 Ono et al. 264210 3,382,307 5/1968 Ciceri et a1 264290X 3,080,345 3/1963 Brooks et al. 26078 3,189,664 6/1965 Nozaki 260857X 3,296,216 1/1967 Snooks 26078 3,287,324 11/1966 Sweeney 26078 3,440,226 4/ 1969 Crovatt et al. 260---78 FOREIGN PATENTS 820,994 9/ 1959 Great Britain 26078 849,788 9/ 1960 Great Britain 26078 DONALD WATKINS, Primary Examiner US. Cl. X.R. 26078; 264210 mg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,555,805 Dated January 19 1971 Inventor(s) Peter Raymond Thomas It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 22, "polyamide" should read ---polymeric--.

Column 1, line 71, "tmeperature" should read ---temperature Column 2, line 70 "0 0 Should be 1 2"- Column 3, line 38, "100.010" should be ---l00 ,0l0--.

Column 5, line 36, (6 :6 :T) should be (6 :6.T)--- Column 8, line 12 "avery" should be ---a very---.

Column 10 Table 1, under Example 4, the sixth line, "3"

should be ---l--.

Column 13, line 55, "hase" should be --base--.

Signed and sealed this 1 7th day of August 1 971 (SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JI Attesting Officer Commissimer of Patent: 

